1. Field of the Invention
The present invention relates to a composition containing a particulate substance, a solvent, and a polymer having an ionic functional group. The present invention relates also to an ink composition comprising the above polymer-containing composition, and an image-forming method and an image-forming apparatus employing the ink composition. In particular, the present invention relates to a pigment-dispersion ink composition which comprises water as the solvent and a pigment as the particulate substance; an image-forming composition useful for printers, displays, and the like; and image-forming method and an image forming apparatus employing the pigment-dispersion ink composition.
2. Related Background Art
Various aqueous liquid dispersions are known which contain a particulate solid matter as functional materials, including pesticides such as herbicides, and insecticides; medicines such as anticancer agents, anti-allergy agents, and anti-inflammatory agents; and particulate substances such as coloring materials like inks and toners containing a colorant. In recent years, digital printing techniques are progressing remarkably rapidly. Typical examples of the digital printing techniques are electrophotographic techniques and ink-jet techniques. Such digital printing techniques are becoming more and more important in offices and homes.
Among the digital printing techniques, the ink-jet recording techniques have remarkable advantages of compactness and less power consumption of the apparatus as a direct recording method, contributing improvement of image quality by using finer nozzles. In an example of the ink-jet technique, an ink fed from an ink tank is vaporized into a bubble by heating in a nozzle to be ejected from the nozzle to form an image on a recording medium. In another example, a piezo element is energized to eject an ink through a nozzle.
In these methods, since the ink employed is usually an aqueous dye solution, the ink can run on superposition of colors, or the ink can feather in the fiber direction of the paper in the recorded area of the recording medium. For prevention thereof, use of a pigment-dispersion ink is investigated (U.S. Pat. No. 5,085,698). However, many problems are still remaining unsolved.
The present invention has been made to solve the above problems in the prior art techniques. The present invention intends to provide a composition containing a particulate substance dispersed in a solvent and a block polymer having an ionic functional group.
The present invention intends also to provide an ink composition containing a pigment as the particulate substance, water as the solvent, in which the pigment is dispersed with high dispersibility.
The present invention intends further to provide a pigment-dispersion ink composition for ink-jet recording, which contains a particulate pigment material dispersed with high dispersion stability in the solvent, and which forms an image with high fixability and high smearing resistance.
The present invention intends still further to provide an image-forming method employing the above pigment-dispersion ink composition for ink-jet recording, and an image-forming apparatus for the image-forming method.